I (still) think something like torrent could help with it.

Yes it is not 100% reliable nor fast every time. But you could have both big seeding silos that take almost anything and are run by some rich people that just want to scrape everything or some donation based org. Or if someone really want their content to be available, they will seed it themselves.

Buuuuut apple doesn't allow torrent apps in the store so an universal tight integration of torrent in nostr clients is not on the table rn.